Practical implementation of transmit/receive antenna selection requires a set of switches in the RF front-end able to connect an RF circuit or a limited number of transmit/receive RF chains to a larger number of antennas. Different types of switching devices can be employed, which can be broadly categorized into solid-state based and electro-mechanical based switches. Solid-state switches are those circuits or devices built entirely from solid materials and in which the charge carriers are confined entirely within the solid material. Common solid-state devices include transistors, microprocessor chips etc. Solid-state switches have the main advantage of achieving faster switching rates as well as lower cost and longer life-spans, but this comes at the cost of a relatively large insertion loss. On the other hand electromechanical and especially MEMS (micro electro-mechanical systems) based switches, have a much lower associated insertion loss, but are typically not suitable for antenna switching in cellular systems due to their large switching delays. MEMS switches are surface-micro machined devices which use a mechanical movement to achieve a short circuit or an open circuit in the RF transmission line
When solid-state switches are employed, insertion loss can negate antenna selection gains. Experimental evaluation by the inventors has shown that, for a practical LTE system performing uplink selection (1 element out of 4) under realistic propagation conditions, gains in the order of 2 dB and up to 3 dB can be achieved before accounting for signal loss in the device, depending on the type of channel and amount of interference present. Considering practical single-pole double-throw switches with 1 dB insertion loss, a total attenuation of 2 dB results, which all but negates the advantages of antenna selection if a noise-dominated scenario is assumed. On the other hand, in interference-loaded cases, signal loss at the switches has a smaller impact on receiver signal to interference plus noise ratio (SINR), hence making it easier for antenna selection to deliver net gains.